1. Field of the Invention
The invention relates generally to apparatus for containing leaks that may develop within a conveyance and delivery system for hazardous and toxic fluids, such as petrochemicals and industrial chemicals. More particularly, the invention pertains to secondary containment systems providing leak detection and total containment for leaks occurring in a pumping station, piping system, or at a dispensing station, for hazardous fluids.
2. The Prior Art
Secondary containment systems for certain hazardous fluid storage, conveyance, and delivery systems have been mandated by governmental agencies in recent years. As a consequence of these regulations, a number of different containment systems have been proposed. The earliest regulations pertained solely to the tanks and containers used to store the fluids. These tanks were typically, but not always, located underground. Double wall tanks and flexible membrane liners for the tank pit were developed to contain leaks which might occur in the primary wall of fluid storage tanks.
Later regulations required secondary containment of the components for conveying and delivering the hazardous fluids from the storage tank to a utilization site. These components may include a pump, adjacent the storage tank, a remote delivery or dispensing station, and a piping system interconnecting the two.
A first construction for secondarily containing these components employs sections of preformed trench liners, connected end to end and laid within an excavated pipe trench. Typical of such trench liner systems is the arrangement shown in U.S. Pat. No. 4,653,958, issued to Anderson et al. In Anderson's containment system, the transverse cross-sectional configuration of each fiberglass trench liner section closely resembles the shape of the pipe trench within which it lies, having a planar bottom wall, or floor, and vertically upstanding side walls. Also disclosed in the Anderson patent are a turbine pump enclosure, a dispenser station catchment pan, a leak sensor, and connector sections, such as elbows, Tees, and the like.
In Moreland, U.S. Pat. No. 4,682,911, a flexible membrane containment system is taught. Moreland's membrane material is designed to be placed within existing fluid storage tank pits, as well as to line and generally conform to the configuration of the pipe trenches which radiate from the pit area. A membrane-lined drip pan, underlying a fluid dispensing station, is also disclosed. Moreland shows the placement of leak monitor stations at low points in the system where fluids may collect. Moreland further uses curved and intersecting sections of membrane material to join straight lengths of the flexible trench liner membrane. The various membrane sections which form the total containment system are connected together by means of plastic zippers.
A third class of secondary containment systems employs double wall piping to confine leaks only occurring within the pipe system. This "pipe within a pipe" construction may use conventional pipe fittings, such as Tees, crosses, elbows, or other angled connectors or fittings, in combination with straight or linear runs of the secondary containment pipe. Another variant of this double wall system utilizes special two-piece fittings at the angled or intersecting connection points in the containment piping. These clamshell-like fittings facilitate assembly of the inner product piping in combination with the outer containment piping. Representative of this latter construction is RED THREAD II, manufactured by A. O. Smith Fiberglass Products, Inc., of Little Rock, Ark.